The present invention relates to a terminal connection device for connecting a primary terminal of a switch or a circuit breaker with a terminal of a fixed frame.
FIG. 7 is a side view showing a conventional terminal connection device, and FIG. 8 is a view (a front view of the terminal connection device) of the terminal connection device shown in FIG. 7 from which the second terminal is pulled out, wherein the view is taken in the direction of arrow A.
FIGS. 9A and 9B are showing a structure of the conventional terminal connecting device shown in FIG. 7. FIG. 9A is a side view of a contact piece of the terminal connecting device described later, and FIG. 9B is a front view of the contact piece of the terminal connecting device. That is, FIG. 9B is a view of the contact piece of the terminal connecting device shown in FIG. 9A, wherein the view is taken in the direction of arrow B.
In the drawings, reference numeral 1 is a first terminal, the shape of which is, for example, a circular rod-shape. The first terminal is, for example, a terminal of a circuit breaker or a switch. Reference symbole "a" is a central axis of the first terminal. Reference numeral 2 is a contact piece arranged outside the first terminal 1.
The contact piece 2 is an electrically conductive member. When a plurality of contact pieces 2 are arranged along the outer circumferential direction on the side of the first terminal being formed into a ring-shape (in this case, a circle), the plurality of contact pieces 2 compose a terminal contact member 21.
Reference symbol R1 is a size of an outer diameter of the terminal contact member 21. Reference numeral 3 is a compression spring which is a pushing means for pushing the contact pieces 2. The compression spring 3 is arranged on the outer circumference of the terminal contact member 21 and presses the contact piece 2 to the first terminal 1 by giving a force from the outside of the contact piece 2 to the inside.
Each compression spring 3 is a ring-shaped spring. When the compression springs 3 are arranged in the recesses 2e to 2g formed in the contact piece 2, a force directed from the outside of the contact piece 2 to the inside can be given to the contact piece 2, that is, a force directed to the central axis "a" of the first terminal 1 can be given to the contact piece 2.
Reference numeral 4 is a first guide plate, and reference numeral 5 is a second guide plate. Reference numeral 6 is a second terminal, the shape of which is formed into a circular rod-shape. The second terminal 6 is, for example, a terminal of a fixing frame (not shown in the drawing) to be connected with a circuit breaker. Reference numeral 8 is a screw which is a fixing means for fixing the first terminal 1 to the first guide plate 4.
When the second terminal 6 is inserted into a space inside the terminal contact member 21 so that the contact piece 2 can be contacted with the second terminal 6, it is possible to attain a condition in which an electrical current flows between the first terminal 1 and the second terminal 6. Therefore, the first terminal 1 and the second terminal 6 are electrically connected with each other.
When the first terminal 1 and the second terminal 6 are electrically disconnected from each other, the second terminal 6 is pulled out from the terminal contact member 21.
At this time, since the contact piece 2 is fixed to the first terminal 1, the contact piece 2 is left on the outer circumference of the first terminal 1. Therefore, the second contact surface 2b become hollow.
In the case of replacing parts arranged on the side of the first terminal 1, after the first terminal 1 and the second terminal 2 have been electrically disconnected from each other, the predetermined parts are replaced.
FIG. 10 is a view showing a structure of the first guide plate 4.
As shown in FIG. 10, the first guide plate 4 is composed in such a manner that a plurality of recesses 4a are formed at regular intervals on the outer circumference of a circular plate.
A plurality of contact pieces 2 are arranged on the outer circumference of the first terminal 1 being formed into a circle when the recesses 2c of the contact pieces 2 are put in the recesses 4a of the first guide plate 4.
Side walls 4b of the recesses 4a prevent the contact pieces 2 from being displaced in the transverse direction or in the outer circumferential direction of the first terminal.
When a screw 8 is put in a screw hole 4c formed on the first guide plate 4, the first guide plate 4 is fixed to the first terminal 1.
FIG. 11 is a view showing a structure of the second guide plate 5.
As shown in FIG. 11, the second guide plate 5 is an annular member composed in such a manner that a plurality of recesses 5a are formed at regular intervals on the outer circumference of the annular member.
A plurality of contact pieces 2 are arranged on the outer circumference of the second terminal 6 being formed into a circle when the recesses 2d of the contact pieces 2 are put in the recesses 5a of the second guide plate 5.
Side walls 5b of the recesses 5a prevent the contact pieces 2 from being displaced in the transverse direction.
Inner diameter R of the second guide plate 5 is determined to be larger than the diameter of the second terminal 6 so that the second terminal 6 can be pulled out.
When the second terminal 6 is pulled out from the terminal contact member 21, a bottom surface of the recess 5a of the second guide plate 5 supports the contact piece 2, and a tip end portion of the contact piece 2 on the contact surface side 2b is prevented from being displaced toward the central axis "a" of the first terminal 1.
FIG. 12 is a schematic illustration showing a distribution of forces given to the contact piece 2.
In FIG. 12, RA is a pushing force given from the first contact surface 2a to the first terminal 1, RB is a pushing force given from the second contact surface 2b to the second terminal 6, and P is a pushing force given by the compression spring 3.
When the compression springs 3 are arranged at regular intervals as shown in the drawing, pushing force RA given between the first terminal 1 and the contact piece 2 becomes equal to pushing force RB given between the second terminal 6 and the contact piece 2.
In order to prevent the tip end portion of the contact piece 2 on the second contact surface 2b side from being displaced toward the central axis "a" of the first terminal 1 when the second terminal 6 is pulled out and in order to support the tip end portion of the contact piece 2 on the second contact surface 2b side, the first guide plate 4 and the second guide plate 5 are used in the conventional terminal connection device. However, in the above conventional terminal connection device, there is caused a problem that the number of parts composing the terminal connection device is increased.
In addition when the two guide plates are integrated into one, an amount of displacement of the tip end portion of the contact piece 2 on the second contact surface 2b side toward the central axis of the first terminal is increased too much after the second terminal 6 has been pulled out. Therefore, it becomes impossible to insert the second terminal 6 again.